1. Field of the Invention
Embodiments of the present invention generally relate to an apparatus and a method for distributing a process gas in a vacuum chamber. More particularly, this invention relates to an apparatus and a method for distributing a process gas in a vacuum chamber suitable for depositing silicon-containing films and the like.
2. Description of the Related Art
Plasma display panels and liquid crystal displays are frequently used for flat panel displays. Liquid crystal displays (LCD) generally contain two glass substrates joined together with a layer of a liquid crystal material sandwiched therebetween. The glass substrate may be a semiconductor substrate, or may be a transparent substrate such as a glass, quartz, sapphire, or a clear plastic film. The LCD may also contain light emitting diodes for back lighting.
As the size requirements for liquid crystal displays have increased, the ability to deposit certain films having both acceptable film properties and acceptable film thickness uniformity within the same film has become increasingly difficult to achieve. FIG. 1 depicts a sectional view of a conventional thin film transistor (TFT) device structure 100 disposed on a substrate 102. A dielectric layer 104 may be optionally disposed on the substrate 102. Subsequently, a gate electrode 106 is formed and patterned on the dielectric layer 104 followed by a gate insulator layer 108. A semiconductor layer of amorphous silicon (a-Si) 110 is usually formed on the gate insulator layer 108 followed by a thin doped semiconductor layer of n-type or p-type amorphous silicon layer (N+/P+-a-Si) 112. After formation of the doped semiconductor layer 112, a source-drain metal electrode layer 114 is then disposed thereon to form the TFT device structure 100.
During deposition, process recipes are selected to deposit films with the most advantageous balance of film properties and film thicknesses. However, processes that produce the most desirable film properties are often achieved at the expense of the control of film thickness. For smaller large area substrates, the balance between good film properties and good film thickness uniformity was satisfactorily managed. However, conventional deposition processes which compromise film property and thickness cannot produce a film of sufficient quality to meet device performance requirements for larger large area substrates, i.e., substrates approaching and exceeding 40,000 cm2 in plan area.
Therefore, there is a need for an improved apparatus and method for depositing a film having good film properties and thickness uniformity.